Megalania ("great roamer") is a giant extinctgoanna or monitor lizard. It was part of a megafaunal assemblage that inhabited southern Australia during the Pleistocene, and appears to have disappeared around 40,000 years ago. The first aboriginal settlers of Australia may have encountered living Megalania.[2]

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The name Megalania prisca was coined by Sir Richard Owen to mean "Ancient Great Roamer." A name he made "in reference to the terrestrial nature of the great Saurian" [1]. To do this Owen used a modification of the Greek word ἠλαίνω ēlainō ("I roam"). The close similarity to the Latin word: lania (femine form of "butcher"), resulted in numerous taxonomic and popular descriptions of Megalania mistranslating the name as: Ancient Giant Butcher.

Megalania prisca was originally classified in its own monotypicgenus. Its status as a valid genus remains controversial, with many authors preferring to consider it a junior synonym of Varanus[3], which encompasses all living monitor lizards. As the gender of the genera Megalania and Varanus are different (feminine and masculine, respectively), the epithet prisca changes to priscus (in alignment with the Code of the I.C.Z.N.) [4].

The lack of complete, or nearly complete fossil skeletons has made it difficult to determine the exact dimensions of Megalania[3]. Early estimates placed the length of the largest individuals at 7 metres (23 ft), with a maximum weight of approximately 600–620 kilograms (1,300–1,400 lb).[5] However, more recent and more rigorous studies give very different results from one another.

In 2002, Stephen Wroe determined that Megalania had a maximum length of 4.5 metres (15 ft) and a weight of 331 kilograms (730 lb)[6], while its average length would have been around 3.5 metres (11 ft), and mean body weight would have been between 97–158 kilograms (210–350 lb).[6][7] He concluded[6] that the earlier estimates reaching lengths of 6 metres (20 ft) or more and a weight of several tons[8][9] were exaggerations based upon flawed methodologies.

However, Ralph Molnar [3] in 2004 determined a range of potential sizes for Megalania (made by scaling up from dorsal vertebrae, after he determined a relationship between dorsal vertebrae length and total body length). If it had a long thin tail like the Lace monitor (Varanus varius), then it would reached a length of 7.9 metres (26 ft), while if its tail-to-body proportions were more similar to that of the Komodo dragon, then a length of around 7 metres (23 ft) is more likely. Taking the maximal 7 m length, he estimated a weight of 1,940 kilograms (4,300 lb), with a leaner 320 kilograms (710 lb) being average[3].

Megalania is the largest terrestrial lizard known to have existed. Judging from its size, Megalania would have fed mostly upon medium to large sized animals, including any of the giant marsupials like Diprotodon along with other reptiles, small mammals, and birds and their eggs and chicks.[citation needed] It had heavily built limbs and body and a large skull complete with a small crest in between the eyes, and a jaw full of serrated blade-like teeth [4].

Several studies have attempted to establish the phylogenetic position of Megalania within the Varanidae. An affinity with the Perentie, Australia's largest living lizard, has been suggested based on skull-roof morphology [10]. The most recent comprehensive study [11] proposes a sister-taxon relationship with the Komodo Dragon based on neurocranial similarities, with the Lace Monitor as the closest living Australian relative. Conversely, the Perentie is considered more closely related to the Gould's and Argus Monitors.

Wroe et al. (1999)[12] regard the contention that Megalania was the only, or even principal, predator of the Australian Pleistocene megafauna with skepticism. They note that the marsupial lion (Thylacoleo carnifex) has been implicated with the butchery of very large Pleistocene mammals, while Megalania has not. In addition, they note that fossils of Megalania are extremely uncommon, in contrast to Thylacoleo carnifex with its wide distribution across Australian Pleistocene deposits.

The Australian biologist Tim Flannery suggested that if one wanted to reconstruct the ecosystems that existed before the arrival of the humans on Australia, it may be desirable to introduce Komodo dragon as a replacement for Megalania.[13]

There have been numerous reports and rumors of living Megalania in Australia, and occasionally in New Guinea, as recently as the late 1990s[14]. Australian cryptozoologistRex Gilroy has stated that Megalania is still alive today, and it is only a matter of time until one is discovered alive.[15]

The possibility of a surviving population of the giant lizards in the Australian Outback is not accepted by mainstream scientists[16], as reports of giant lizards only began after Megalania was first described.

^Hecht, M. 1975. The morphology and relationships of the largest known terrestrial lizard, Megalania prisca Owen, from the Pleistocene of Australia. Proceedings of the Royal Society of Victoria87: 239–250.

^ abcWroe, S. 2002. A review of terrestrial mammalian and reptilian carnivore ecology in Australian fossil faunas, and factors influencing their diversity: the myth of reptilian domination and its broader ramifications. Australian Journal of Zoology50: 1–24.